This relates to video processing pipelines that convert interlaced to progressive scan or de-interlaced video.
For a variety of applications, interlaced video signal frames are converted to a progressive scan format. Interlaced video includes fields with only odd or even lines of video. For example, interlaced signal received over the air may be converted to a progressive scan format for display on a digital video monitor. The conversion generally involves interpolating the missing lines of video, either even or odd, in each interlaced video field.
A number of de-interlacing techniques have been proposed. According to an inter-field technique known as “weave”, the interpolated pixel is taken from the corresponding pixel in the previous field. This technique may result in artifacts when there is motion in the video signal at the point of interpolation.
According to an intra-field technique known as “bob”, the pixel value to be generated is interpolated from the two pixels in the same field which are respectively directly above and directly below the pixel to be generated. This technique may result in loss of resolution and creation of certain artifacts.
In another technique, sometimes referred to as “motion adaptive” de-interlacing, motion detection is applied at the point where interpolation is occurring. If there is no motion, a “weave” approach is applied. If there is motion at the current point, a “bob” approach is applied. In another proposed motion adaptive de-interlacing technique, the pixel value to be generated is obtained as a weighted average of the pixel values that would be obtained by the “bob” and “weave” approaches, and the weights applied to the bob and weave pixel values vary depending on the degree of motion. Even with these approaches, however, image quality may be less than ideal.
Another technique is known as “motion compensated” de-interlacing. In this approach, motion between the current field and the previous field is estimated to produce motion vectors at, for example, each pixel location. Then interpolation is performed using pixels from the previous frame that have been relocated in accordance with the motion vectors. Motion compensated de-interlacing generally produces superior results in terms of image quality, but requires a high degree of processing complexity, and may still fall short of an ideal level of image quality.